The present invention relates to a release device for actuating a clamping device for tools, the release device comprising at least one release element movable by a drive from a rest position into a release position in which it moves a draw bar of the clamping device against a clamping force into a disengaged position.
Clamping devices are used for clamping tools at an interface of a tool spindle. The tool spindle generally has a HSK (“Hohischaftkegel”=hollow shank taper) receptacle for the tools that are drawn by a collet chuck into the spindle and clamped with a high axial drawing force. By the axial movement of the draw bar, the collet chuck segments are forced outwardly by means of a conical member seated on the draw bar. The collet chuck elements engage a clamping surface of the tool that is drawn by the draw bar into the spindle and clamped. The axial movement of the draw bar in the clamping direction is mechanically realized very safely and reliably by a spring packet, for example, a disk spring or plate spring packet.
In order to release the tool, the draw bar must be moved forwardly against the spring force. The collet chuck segments are released such that they can pivot inwardly. The tool is then ejected out of the tool receptacle across the remainder of the travel path by the draw bar. For axially moving the draw bar for releasing the tool, a release device is provided that is configured as a hydraulically actuatable release device embodied similar to a hydraulic cylinder. In order to exert during release no force or only minimal force onto the spindle bearing, a part of the release device is axially movably arranged in a receptacle and is axially supported by a coupling ring on a coupling screw seated in the tool spindle. In this way, the flow of forces when releasing the tool is not passing through the bearing but through this support.
It is also known to pneumatically actuate similar release devices.
The solution based on hydraulics is complex and expensive because of the need for a hydraulic unit with pump, oil container, valve block and the required conduit system. Moreover, leakage can cause functional disruptions. When the tool spindle is driven by belts, the hydraulic lines must be separated for changing the belts; this is difficult even when using hydraulic quick couplings and partially leads to soiling by oil.
The solution based on pneumatics operates without the medium oil but has otherwise the same disadvantages as the solution based on hydraulics. Moreover, the pneumatically operating release device, as a result of the relatively low pressures, must either be constructed to be very large for providing the required great forces or expensive special solutions are required, for example, double cylinders or pressure transmitters.